Fluted coulters or discs, for example as shown in U.S. Pat. No. 4,538,688 to Szucs et al., has an outer peripheral cutting surface and flutes 17/27/37/51/61/81 that extend radially outwardly from a respective center flat portion 14/24/34/44/54/64/74/84 that has a respective central opening 15/25/3545/55/65/75/85. From the point of view of strength of the Szucs et al. blades, anywhere that the metal of the disc/coulter has been changed from being flat as it started out from in the manufacturing process, is going to be weaker than that part of the blade that has not been changed from flat. And that portion of the blade where any abrupt change from flat occurs is going to be the weakest part of the blade and consequently the most likely place for the blade to break if subjected to extreme forces such as when the blade hits a large rock in a farm field during use.
Simpler blades like that shown in U.S. Pat. No. 1,663,239 to Bucknam, U.S. Pat. No. 2,291,722 to Ingersoll and British Patent Specification No. 832,431 to Gheraldo have circular bends on radially inner diameters compared, for example, to a simple convex/concave disc of the well known common type shown in U.S. Pat. No. 4,072,197 to Boyd-Dunlop.
So if the discs shown in U.S. Pat. No. 1,663,239 to Bucknam, U.S. Pat. No. 2,291,722 to Ingersoll and British Patent Specification No. 832,431 to Gheraldo hit a large rock in the field and break, the break will of course be at the weakest place on the disc which is at the circular area where the sharpest bends of the respective discs are located. When such a disc hits a rock, the greatest moment arm (thereby causing the greatest breaking forces) will be from where the disc hit the rock on the outside periphery of the disc to the radially innermost weakest part of the disc where the flat plate abruptly changes from flat to some other shape. This weakest part is radially outwardly from the center of rotation of the disc to the most radially inward place where one of the abrupt bend of the plate/disc occurs, such as at 16 of Buckman, 18 of Ingersoll and 18 or 11 of Gheraldo or the radially innermost place on the Szucs et al. coulters where the flat part of the coulter is bent, for example.
If the simple convex/concave disc of the well known common type that has been used for over a century like that shown in U.S. Pat. No. 4,072,197 to Boyd-Dunlop hits a big rock hard enough, it will break, but it is not predictable where the break will occur in the blade because the curvature is constant throughout the entire blade except for the sharpened portion on the extreme outer periphery thereof.
All of the aforementioned prior art documents are incorporated herein by reference in their entirety.
Accordingly, there is a need for a disc, coulter or planter blade that is stronger than those available in the past due simply to the configuration thereof.